Delay-rate tradeoff in ergodic interference alignment

TL;DR

This paper introduces new schemes called JAP and JAP-B that reduce the delay in ergodic interference alignment for multi-user networks, balancing delay and rate more effectively.

Contribution

It presents two new families of schemes that lower the expected delay in ergodic interference alignment, with specific analysis for small and large networks.

Findings

Delay scales as q^T with T quadratic in n for large networks.

Half the single-user rate achieved with reduced delay q^(n-1)(n-2).

Schemes are effective for networks with few users.

Abstract

Ergodic interference alignment, as introduced by Nazer et al (NGJV), is a technique that allows high-rate communication in n-user interference networks with fast fading. It works by splitting communication across a pair of fading matrices. However, it comes with the overhead of a long time delay until matchable matrices occur: the delay is q^n^2 for field size q. In this paper, we outline two new families of schemes, called JAP and JAP-B, that reduce the expected delay, sometimes at the cost of a reduction in rate from the NGJV scheme. In particular, we give examples of good schemes for networks with few users, and show that in large n-user networks, the delay scales like q^T, where T is quadratic in n for a constant per-user rate and T is constant for a constant sum-rate. We also show that half the single-user rate can be achieved while reducing NGJV's delay from q^n^2 to q^(n-1)(n-2). This extended version includes complete proofs and more details of good schemes for small n.